This invention relates to a fuel injector for supplying liquid fuel to an air inlet duct of a spark ignition engine, the injector comprising a valve seat member defining an annular seating for engagement by a solenoid actuated valve member, an orifice through which fuel under pressure can flow when the valve member is lifted from the seating and a tubular outlet through which in use fuel flows from the orifice to the air inlet duct.
Such injectors are well known in the art and may be provided with more than one orifice. The fuel flowing through the orifice forms a fuel spray which exits from the outlet to mix with the air flowing in the air inlet duct. In the case where the seat member has more than one orifice the jets of fuel leaving the orifices may impinge on each other to provide a special spray pattern. Care is taken to ensure that the fuel spray leaving the orifice or orifices does not impinge on the side wall of the outlet unless a special spray pattern is required. However, since a precise spray pattern is not produced some droplets of fuel do impinge on the wall of the outlet and the tendency is for the droplets of fuel to coalesce to form a larger drop which eventually fails into the air inlet duct. The tendency for this to happen increases as the inclination of the longitudinal axis of the nozzle from the vertical increases. The large drops of fuel do not mix properly with the air flowing to the engine cylinders and simply wet the surface of the air inlet duct thereby causing combustion problems.
Moreover, in injectors in which the diameter of the outlet is small, fuel can accumulate within the outlet thereby impairing and in some cases inhibiting the formation of a fuel spray.